Avoid a useless JSON serialization of the data

drag_and_drop_v2/drag_and_drop_v2.py

@@ -135,14 +135,7 @@ class DragAndDropBlock(XBlock):
         self.display_name = submissions['display_name']
         self.question_text = submissions['question_text']
         self.weight = float(submissions['weight'])
-
-        try:
-            self.data = json.loads(submissions['data'])
-        except ValueError as e:
-            return {
-                'result': 'error',
-                'message': e.message
-            }
+        self.data = submissions['data']
 
         return {
             'result': 'success',

drag_and_drop_v2/public/js/drag_and_drop_edit.js

@@ -356,7 +356,7 @@ function DragAndDropEditBlock(runtime, element) {
                             'display_name': $(element).find('.display-name').val(),
                             'weight': $(element).find('.weight').val(),
                             'question_text': $(element).find('.question-text').val(),
-                            'data': JSON.stringify(_fn.data),
+                            'data': _fn.data,
                         };
 
                         $('.xblock-editor-error-message', element).html();